Re: [PATCH 2/2] clk: uniphier: add clock data for cpufreq

From: Stephen Boyd
Date: Wed Nov 23 2016 - 21:11:46 EST


On 11/24, Masahiro Yamada wrote:
> Hi Stephen,
>
>
> 2016-11-24 9:05 GMT+09:00 Stephen Boyd <sboyd@xxxxxxxxxxxxxx>:
>
> >> +#if 1
> >> + /*
> >> + * TODO:
> >> + * The return type of .round_rate() is "long", which is 32 bit wide on
> >> + * 32 bit systems. Clock rate greater than LONG_MAX (~ 2.15 GHz) is
> >> + * treated as an error. Needs a workaround until the problem is fixed.
> >> + */
> >
> > Just curious is the problem internal to the clk framework because
> > of the clk_ops::round_rate design? Or does the consumer, cpufreq
> > in this case, have to deal with rates that are larger than
> > unsigned long on a 32 bit system? If it's just a clk_ops problem
> > and we need to support rates up to 32 bits wide (~ 4.3 GHz) on
> > the system then the driver could be changed to use
> > .determine_rate() ops and that would allow us to use all the bits
> > of unsigned long to figure out rates.
> >
> > If the problem is rates even larger than unsigned long on 32 bit
> > systems, then at the least I'd like to see some sort of plan to
> > fix that in the framework before merging code. Hopefully it can
> > be done gradually, but as I start looking at it it seems more and
> > more complicated to support this so this will be a long term
> > project.
> >
> > We can discuss the clk API changes needed as well if those are
> > required, but that is another issue that requires changes in
> > other places outside of clk drivers.
> >
>
> I understand your point, but core frame-work changes
> need more careful review than clk data changes in low-level drivers.
> It is too late to be included in v4.10.
>
> If I drop 32bit SoC things, and send v2 only for 64bit SoCs,
> is that acceptable for 4.10-rc1?

Sure. That sounds fine for now. I'll reply to your other thread
with a plan of attack on how to do the framework changes. I think
we need to do those regardless of the outcome of your
investigation.

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